/* origin: FreeBSD /usr/src/lib/msun/src/e_atan2l.c */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 *
 */
/*
 * See comments in atan2.c.
 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
 */

#include "libc/math/__invtrigl.h"
#include "libc/math/libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double atan2l(long double y, long double x) { return atan2(y, x); }
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384

long double atan2l(long double y, long double x) {
  union ldshape ux, uy;
  long double z;
  int m, ex, ey;

  if (isnan(x) || isnan(y)) return x + y;
  if (x == 1) return atanl(y);
  ux.f = x;
  uy.f = y;
  ex = ux.i.se & 0x7fff;
  ey = uy.i.se & 0x7fff;
  m = 2 * (ux.i.se >> 15) | uy.i.se >> 15;
  if (y == 0) {
    switch (m) {
      case 0:
      case 1:
        return y; /* atan(+-0,+anything)=+-0 */
      case 2:
        return 2 * pio2_hi; /* atan(+0,-anything) = pi */
      case 3:
        return -2 * pio2_hi; /* atan(-0,-anything) =-pi */
    }
  }
  if (x == 0) return m & 1 ? -pio2_hi : pio2_hi;
  if (ex == 0x7fff) {
    if (ey == 0x7fff) {
      switch (m) {
        case 0:
          return pio2_hi / 2; /* atan(+INF,+INF) */
        case 1:
          return -pio2_hi / 2; /* atan(-INF,+INF) */
        case 2:
          return 1.5 * pio2_hi; /* atan(+INF,-INF) */
        case 3:
          return -1.5 * pio2_hi; /* atan(-INF,-INF) */
      }
    } else {
      switch (m) {
        case 0:
          return 0.0; /* atan(+...,+INF) */
        case 1:
          return -0.0; /* atan(-...,+INF) */
        case 2:
          return 2 * pio2_hi; /* atan(+...,-INF) */
        case 3:
          return -2 * pio2_hi; /* atan(-...,-INF) */
      }
    }
  }
  if (ex + 120 < ey || ey == 0x7fff) return m & 1 ? -pio2_hi : pio2_hi;
  /* z = atan(|y/x|) without spurious underflow */
  if ((m & 2) && ey + 120 < ex) /* |y/x| < 0x1p-120, x<0 */
    z = 0.0;
  else
    z = atanl(fabsl(y / x));
  switch (m) {
    case 0:
      return z; /* atan(+,+) */
    case 1:
      return -z; /* atan(-,+) */
    case 2:
      return 2 * __pio2_hi - (z - 2 * pio2_lo); /* atan(+,-) */
    default:                                    /* case 3 */
      return (z - 2 * __pio2_lo) - 2 * pio2_hi; /* atan(-,-) */
  }
}
#endif
